Symmetrical bis(unsymmetrical tertiary-alkyl and tertiary- aralkyl azo) compounds

ABSTRACT

Novel symmetrical bis(unsymmetrical t-alkyl and t-aralykl azo) compounds of the general formula I: 
     
         R -- N = N -- R.sub.12 -- N = N -- R&#39;                      (I) 
    
     wherein R = R&#39; = (R&#34;) 3  C--, e.g., 1,2-ethylene bis(4-t-butylazo-4-cyanovalerate); and the use of I for sequential generation of free radicals, e.g. styrene monomer and 1,2-ethylene bis(4-t-butylazo-4-cyanovalerate) are reacted to obtain polystyrene containing attached azo groups which in turn is reacted with methyl methacrylate monomer to obtain a block copolymer of polystyrene and poly(methyl methacrylate).

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a division, of application Ser. No. 88,247, filed Nov. 9, 1970,which in turn is a continuation-in-part of application Ser. No. 725,180(now abandoned), filed Apr. 29, 1968, which is a continuation ofapplication Ser. No. 616,158, filed Feb. 15, 1967 (now abandoned), whichis a continuation of application Ser. No. 409,306, filed Nov. 5, 1964(now abandoned) of Chester S. Sheppard et al.

BACKGROUND OF THE INVENTION

This invention relates to new symmetrical bis(unsymmetrical t-alkyl ort-aralkyl azo) compounds (wherein "t" is tertiary) and to synthesis oforganic compounds utilizing these novel compounds as sequential freeradical initiators, especially to the preparation of polymers containingattached aliphatic azo groups and to block copolymerization using suchazo-containing polymers.

Heretofore most syntheses which required sequential free radicalinitiation utilized two or more different compounds capable of providingfree radicals; the compounds being selected to provide free radicals atdifferent conditions as called for by the reaction. Commonly compoundsfalling into different chemical classes are used.

Bis azo compounds have been known for sometime. Examples of aliphaticbis phenylazos have been prepared. Preparation oftrans-1,2-bis-phenylazocyclohexane ##SPC1##

Is disclosed by A. J. Bellamy et al., J. Chem. Soc., part C, Org.(1966), 1989 - 1993. Preparation of t-butyl-bis(phenylazo)methane##EQU1## is disclosed by F. Neugebauer et al., Liebigs Ann. Chem. 706,107 - 111 (1967). Other bis azo compounds are likewise disclosed in U.S.Pat. No. 2,554,141, in U.S. Pat. No. 3,244,692 and in C. G. Overbergeret al., J. Am. Chem. Soc. 80, 6556 (1958) and 77, 4651 (1955). None ofthese compounds are closely related to applicants novel bis-azocompounds.

SUMMARY OF THE INVENTION

This invention relates to:

A. novel symmetrical bis(unsymmetrical t-alkyl or t-aralkyl azo)compounds of structure I:

    R -- N = N -- R.sub.12 -- N = N -- R'

wherein:

R equals R' equals (R")₃ C;

(r")₃ c is a C₄ to C₂₀ t-alkyl, cycloalkyl, alkylcycloalkyl,arylcycloalkyl or aralkyl radical wherein R" is a C₁ to C₈ alkyl, C₇ toC₁₂ aralkyl or C₆ to C₁₄ aryl radical, not more than one R" beingaromatic in each (R")₃ C, and wherein 2 or 3 of said R"s can join withthe tertiary carbon atom to form a cyclo, bicyclo or tricyclo radical ofthree to 12 carbons;

R₁₂ can be ##EQU2## R₁ and R₂ are separately selected from a C₁ to C₈alkyl, C₃ to C₁₂ cyclo-, bicyclo- or tricycloalkyl, C₇ to C₁₂ aralkyl ora 5 to 6 membered heterocyclic radical or, taken together, R₁ and R₂ canform a C₃ to C₁₁ alkylene diradical; one or more of each of the R₁ s andR₂ s can be substituted with lower alkoxy, hydroxy, carboxy,alkoxycarbonyl, acyloxy, halogen, cyano, amido or alkylsulfonatoradicals; and R₁ can also be a C₆ to C₁₄ aryl radical; ##EQU3## ##SPC2##or ##EQU4## R'₁₃ is a C₂ to C₂₀ symmetrical aliphatic, cycloaliphatic,aromatic-aliphatic or aliphatic-cycloaliphatic diradical whichoptionally contains two or more (normally 2 - 6) non-adjacent oxygen,sulfur and/or nitrogen atoms in the backbone structure or, when R₁ isnot phenyl or substituted phenyl, a C₆ to C₁₂ symmetrical aromaticdiradical;

R₁₃ is a symmetrical C₅ to C₁₅ alkyl-cycloalkyl, C₂ to C₁₀ alkylene, C₃to C₁₂ cycloalkylene, C₆ to C₁₂ aryl or C₈ to C₁₅ alkyl-aryl diradical;

R₃ is hydrogen or a C₁ to C₁₀ alkyl (e.g. methyl, butyl, octyl) orcycloalkyl ##SPC3##

radical;

each X" is separately selected from oxygen and sulfur;

R₅ is a C₁ to C₁₀ alkyl or cycloalkyl or C₆ to C₁₂ aromatic radical;

R₆ is a lower alkyl (preferably C₁ to C₄) radical; and

R₁₀ is hydrogen or a C₁ to C₁₀ alkyl or cycloalkyl or C₆ to C₁₂ arylradical, and

B. in the preparation of organic compounds wherein sequential freeradical initiation is utilized, to the improvement of using the novel(I) compounds as the source of the sequential free radical generation,especially to the preparation of azo-containing polymers from compoundsI and monomers having ethylenic unsaturation; and to blockcopolymerization of such azo-containing monomers with other vinylmonomers.

DETAILED DESCRIPTION OF INVENTION

The novel compounds of structure I can be prepared in a variety of ways.Several of the methods are described in the working examples. Forexample an azo compound containing an acylating group such as ananhydride, acid chloride, carboxylic acid or chloroformate may becoupled with an equivalent amount of a difunctional intermediatecontaining reactive groups such as diamines, diols, diphenols anddimercaptans. On the other hand, difunctional compounds such as diacidchlorides, dianhydrides, dicarboxylic acids, diisocyanates, dithioacidchlorides, and dichloroformates may be coupled with an equivalent amountof an azo compound containing a reactive functional group such as analcohol, thiol, phenol or amine. Coupling reactions are well known tothe art and involve well known organic reactions such as esterification,amidation, etherification, carbonate formation and many others.Especially suitable compounds for these coupling reactions are theunsymmetrical t-alkyl or t-aralkyl azo compounds containing acylatingfunctions described in our copending application Ser. No. 667,352, filedSept. 13, 1967.

In some cases it may be beneficial to carry out the coupling reaction onan azo precursor, such as the hydrazo, and then oxidize it to the azoafter the coupling reaction.

Another method of preparing structure I compounds is to react adifunctional salt M₂ Y" with an α-chloro azo compound of generalstructure II ##EQU5## wherein: M is an alkali metal (or alkaline earthmetal in which case MY" would be the reaction); and R, R₁, R₂ and Y" areas defined above.

The sequential decompositions of I can be carried out by a variety oftechniques. The preferred method is to use two different temperatures,wherein at the lower temperature, the reaction is carried out for such atime interval that only a partial decomposition of I is obtained, andsubsequently, the second stage of the reaction is carried out at thehigher temperature to completely decompose the remaining I. Anothermethod is to use the same temperature for both stages, wherein thesecond stage is initiated after the first stage had been carried out fora specified time interval wherein only partial decomposition of I hadoccurred. Other methods of decomposing I either partially or completelythat can be used include irradiation and chemical activation. Thus avariety of techniques can be used to decompose I in sequence.

Depending upon their structure, the 10-hour half-life temperature of theI compound can be varied from below 25°C. to above 160°C. Thus, whenusing thermal decomposition techniques only, the symmetrical bis azocompounds I can be used to generate free radicals in sequence attemperatures from about 20°C. to about 200°C. By employing irradiationor chemical activation techniques, the decomposition temperatures can belowered to below 0°C.

The amount of I that is used in the practice of the present inventionwill depend upon whether the I compound is used to generate freeradicals in sequence for the purpose of supplying reactant species orinitiating species. In the former case, stoichiometric amounts of I areused while in the latter case, relatively smaller amounts are usedranging from 0.005 to 20.0 per cent by weight of the reactants used.

A preferred method of the present invention is to employ the I compoundsas sequential free radical initiators for preparing block copolymers bypartially decomposing I in the presence of at least one monomercontaining ethylenic unsaturation to prepare an azo-containing polymer,i.e., one in which the copolymer contains attached undecomposed azogroups; and subsequently copolymerizing the azo-containing polymer withat least one other vinyl monomer for a time sufficient to complete thedecomposition of the undecomposed azo portion of said azo-containingpolymer. Standard polymerization techniques are used such as emulsion,suspension, solution and bulk free radical polymerizations.

Any ethylenically unsaturated monomer capable of being polymerized byfree radical initiation can be used in the first step of the preferredblock copolymer process. Illustrative are the vinyl-type monomers (e.g.styrene) and the conjugated dienes (e.g. butadiene, isoprene,chloroprene and hexadiene).

The expression "vinyl monomer" includes all those organic compoundscontaining at least one CH₂ =C< group in their molecule. Examples ofthese monomers are styrene, alpha-methylstyrene, dichlorostyrene, vinylnaphthalene, vinyl phenol, acrylic acid and the alpha-alkyl substitutedacrylic acids; the esters of these unsaturated acids, such as methylacrylate, methyl methacrylate, butyl methacrylate, and propyl acrylate;the vinylidene halides, such as vinylidene chloride, vinylidene bromideand vinylidene fluoride; vinyl esters of the inorganic acids, such asthe halogen acids and hydrocyanic acid, as vinyl chloride, vinylbromide, acrylonitrile, and methacrylonitrile; the vinyl esters of themonocarboxylic acids, such as vinyl acetate, vinyl chloroacetate, vinylbenzoate, vinyl valerate, and vinyl caproate; the vinyl esters of thepolycarboxylic acids, such as divinyl succinate, divinyl adipate, vinylallyl phthalate, vinyl methallyl pimelate, and vinyl methyl glutarate;the vinyl esters of the unsaturated acids, such as vinyl acrylate, vinylcrotonate, and vinyl methacrylate; the vinyl ethers, such as vinyl ethylether, vinyl butyl ether, and vinyl allyl ether; the vinyl ketones, suchas vinyl butyl ketone, and vinyl ethyl ketone; and the allylderivatives, such as allyl acetate, allyl butyrate, diallyl phthalate,diallyl adipate, methallyl propionate, allyl chloride, methallylchloride, allyl acrylate, and methallyl methacrylate. The conjugateddienes, such as butadiene and chloroprene, are suitable.

Block copolymers are useful as compatibilizing agents for normallyincompatible polymers.

Many novel compounds of the present invention are taught in the workingexamples. Some additional typical compounds of the general structure R-- N = N -- R₁₂ -- N = N -- R' which can be similarly prepared areillustrated below and many more will be obvious to those skilled in theart: ##SPC4## ##EQU6## ##SPC5## ##SPC6## ##SPC7## ##SPC8## ##SPC9####SPC10## ##SPC11## ##SPC12## ##SPC13## ##SPC14## ##SPC15## ##SPC16####SPC17## ##SPC18##

EXAMPLES

Numerous illustrative embodiments of this invention are presented below,but are not to be considered in limitation thereof.

EXAMPLE 1 Preparation of 1,2-Ethylene Bis (4-t-butylazo-4-cyanovalerate)##EQU7##

To a stirred solution of 3.1 grams (.05 moles) of ethylene glycol and 10mls. of pyridine in 100 mls. of methylene chloride in a 250 ml. flaskwas added 22.9 grams (0.1 moles) of 4-t-butylazo-4-cyanovaleryl chlorideover one-half hour holding the temperature at 15°-20°C with a cold waterbath. After the addition was complete, the reaction mixture was thenwashed with water, 5% HCl, water, saturated NaHCO₃ solution, dried overanhydrous Na₂ SO₄, filtered, and the methylene chloride evaporated underreduced pressure leaving 21.7 grams (97% yield) of a light yellowliquid. The infrared spectrum was in agreement with the structure of thedesired compound with the exception of a small amount of unreacted acidchloride. The product was purified by passing it through an aluminacolumn using pentane as the eluent.

EXAMPLE II Block Copolymer From 1,2-Ethylene Bis(4-t-butylazo-4-cyanovalerate)

I. Preparation of Azo-containing Polystyrene

There was charged into a pyrex tube 1.0 grams of 1,2-ethylenebis(4-t-butylazo-4-cyanovalerate) of Example 1 and 20 grams of freshlydistilled styrene monomer. The tube was flushed with nitrogen, sealedand heated to 70°C for 8 hours at which time the reaction was stopped.The polymer was dissolved in benzene and precipitated from methanol.After 3 reprecipitations by a similar technique, the polymer (A) wasdried and weighed. The conversion to polystyrene was 90%.

II. Preparation of Block Polymer

A solution of 1.0 g. polymer (A) and 2.0 g. methyl methacrylate wasadded to a 16 × 150 mm. pyrex test tube. The tube was flushed withnitrogen, sealed and heated to 90°C for 1 hour at which time reactionwas complete. Copolymer (B) was dissolved in benzene and precipitatedfrom methanol twice and dried under vacuum.

III. Compatibility Test

To a 16 × 150 mm. test tube was added the following chloroformsolutions: 3.0 g. of a 13% polystyrene (Dow PS-3) solution, 3.0 g. of a13% polymethyl methacrylate (Acryloid A-11, Rohm & Hass) solution and3.0 g. of a 13% solution of copolymer (B). The tube was sealed andcontents mixed thoroughly. A control mixture, containing only 13%chloroform solutions of the two homopolymers was prepared in a similarmanner.

The control mixture demixed to form two layers in 0.5 to 1 hour whilethe mixture containing copolymer (B) remained stabilized for greaterthan 11 days.

EXAMPLE III Preparation of 1,4-ButyleneBis(4-t-butylazo-4-cyanovalerate) ##EQU8##

To a stirred solution of 1.9 grams (.0211 moles) of 1,4-butanediol and 4mls. of pyridine in 45 mls of diethyl ether in a 100 ml. flask was added9.7 grams (.0422 moles) of 4-t-butylazo-4-cyanovaleryl chloride over 5minutes holding the temperature at 25°-30°C with a water bath. After theaddition was complete, the reaction was stirred an additional 3 hours atroom temperature. The reaction was diluted with water to dissolve thepyridine hydrochloride and the ether layer separated. The ether layerwas washed with 5% HCl, water, saturated NaHCO₃ solution, dried overanhydrous Na₂ SO₄, filtered and the ether evaporated under reducedpressure to leave 9.15 grams (91% yield) of a light brown liquid. Thecrude product was purified by passing it through an alumina column usingpentane as the eluent. The purified material weighed 5.7 grams and itsinfrared spectrum was in agreement with that of the desired compound.

EXAMPLE IV Block Copolymer From 1,4-ButyleneBis(4-t-butylazo-4-cyanovalerate)

I. Preparation of Azo-containing Polystyrene

There was charged into a pyrex tube 1.0 g. of 1,4-butylenebis(4-t-butylazo-4-cyanovalerate) of Example III and 20 grams of freshlydistilled styrene monomer. The tube was flushed with nitrogen, sealedand heated to 70°C for 8 hours at which time the reaction was stopped.The polymer was dissolved in benzene and precipitated from methanol.After another reprecipitation by a similar technique, the polymer (C)was dried and weighed. The conversion to polystyrene was 90%.

II. Preparation of Block Polymer

A solution of 1.0 g. polymer (C) and 2.0 g. methyl methacrylate wasadded to a 16 × 150 mm. pyrex test tube. The tube was flushed withnitrogen, sealed and heated to 90°C for 1 hour at which time reactionwas complete. Copolymer (D) was dissolved in benzene and precipitatedfrom methanol twice and dried under vacuum.

III. Compatibility Test

To a 16 × 150 mm. test tube was added the following chloroformsolutions: 3.0 g. of a 13% polystyrene (Dow PS-3) solution, 3.0 g. of a13% polymethyl methacrylate (Acryloid A-11, Rohm & Hass) solution and3.0 g. of a 13% solution of of copolymer (D). The tube was sealed andcontents mixed thoroughly. A control mixture, containing only 13%chloroform solutions of the two homopolymers was prepared in a similarmanner.

The control mixture demixed to form two layers in 0.5 to 1 hour whilethe mixture containing copolymer (D) remained stabilized for greaterthan 14 days.

EXAMPLE V Preparation of Di(4-t-butylazo-4-cyanopentyl) Sebacate##EQU9##

To a solution of 5.60 grams (.0286 moles) of 4-t-butylazo-4-cyanopentylalcohol (prepared from t-butylhydrazine, NaCN and 1-acetyl-3-propanol)and 2 mls. of pyridine in 25 mls. of ether in a 100 ml. flask was added3.42 grams (.0143 moles) of sebacoyl chloride over 5 minutes, holdingthe temperature at 25°-30°C with a water bath. After the addition wascomplete, the reaction was stirred for an additional 2 hours at roomtemperature. The reaction mixture was then diluted with water, the etherlayer separated and washed with 5% HCl, water, saturated NaHCO₃solution, dried over anhydrous sodium sulfate, filtered and the etherevaporated under reduced pressure. The crude product was a clear yellowliquid weighing 7.25 grams (91% yield). The crude product was purifiedby passing it through an alumina column using benzene as the eluent. Theinfrared spectrum of the purified material was in agreement with thestructure of the desired compound.

EXAMPLE VI Block Copolymer From Di(4-t-butylazo-4-cyanopentyl) Sebacate

I. Preparation of Azo-containing Polystyrene

There was charged into a pyrex tube 1.0 g. ofdi(4-t-butylazo-4-cyanopentyl) sebacate of example V and 20 grams offreshly distilled styrene monomer. The tube was flushed with nitrogen,sealed and heated to 70°C for 8 hours at which time the reaction wasstopped. The polymer was dissolved in benzene and precipitated frommethanol. After another reprecipitation by a similar technique, thepolymer (E) was dried and weighed. The conversion to polystyrene was90%.

II. Preparation of Block Polymer

A solution of 1.0 g. of polymer (E) and 2.0 g. methyl methacrylate wasadded to a 16 × 150 mm. pyrex test tube. The tube was flushed withnitrogen, sealed and heated to 90°C for 1 hour at which time reactionwas complete. Copolymer (F) was dissolved in benzene and precipitatedfrom methanol twice and dried under vacuum.

III. Compatibility Test

To a 16 × 150 mm. test tube was added the following chloroformsolutions: 3.0 g. of 13% polystyrene (Dow PS-3) solution, 3.0 g. of a13% polymethyl methacrylate (Acryloid A-11, Rohm and Hass) solution and3.0 g. of a 13% solution of copolymer (F). The tube was sealed andcontents mixed thoroughly. A control mixture containing only 13%chloroform solutions of the two homopolymers was prepared in a similarmanner.

The control mixture demixed to form two layers in 0.5 to one hour whilethe mixture containing copolymer (F) remained stabilized for greaterthan 14 days.

EXAMPLE VII Preparation of Ethylene Bis(4-t-butylazo-4-methoxypentylcarbonate) ##EQU10##

To a solution of 1.6 grams (.006 moles) of 4-t-butylazo4-methoxypentylchloroformate* in 20 ml. of pentane in a 100 ml. round bottom flask wasadded a solution of 0.19 grams (.003 moles) of ethylene glycol and 0.5grams (.006 moles) of pyridine in 10 mls. of methylene chloride dropwiseover 1 hour. The reaction was stirred an additional one-half hour andthen 10 ml. of cold water added. The organic layer was separated, washedwith 5% HCl, water, saturated NaHCO₃ solution, dried over anhydrous Na₂SO₄, filtered and the solvent evaporated to leave 0.9 grams (60%) of alight yellow liquid. The infrared spectrum was in agreement with thestructure of the desired product.

EXAMPLE VIII Preparation of Ethylene Bis[4-t-butylazo-4-(p-t-butylthiophenoxy)pentyl carbonate] ##SPC19##

To a solution of 3.6 grams (.009 moles) of4-t-butylazo4-(p-t-butylthiophenoxy)pentyl chloroformate in 25 mls. ofpentane in a 100 ml. round bottom flask was added a solution of 0.27grams (.0045 moles) of ethylene glycol and 0.65 grams (.009 moles) ofpyridine in 10 ml. of methylene chloride dropwise over 1 hour. Thereaction was stirred an additional one-half hour and then 10 ml. of coldwater added. The organic layer was separated washed with 5% HCl, water,saturated NaHCO₃ solution, dried over anhydrous Na₂ SO₄, filtered andthe solvent evaporated to leave 2.6 grams (73%) of a yellowish brownviscous liquid. The infrared spectrum was in agreement with thestructure of the desired product.

EXAMPLE IX Preparation of Ethylene Bis(4-t-butylazo-4-thiocyanopentylcarbonate) ##EQU11##

To a solution of 1.3 grams (.0045 moles) of4-t-butylazo-4-thiocyanopentyl chloroformate in 25 mls. of pentane in a100 ml. round bottom flask was added a solution of 0.14 grams (.0022moles) of ethylene glycol and 0.35 grams (.0045 moles) of pyridine in 10mls. of methylene chloride over one-half hour and then 10 ml. of coldwater added. The organic layer was separated, washed with 5% HCl, water,saturated NaHCO₃ solution, dried over anhydrous Na₂ SO₄, filtered andthe solvent evaporated to leave 1.2 grams (96% yield) of a light yellowliquid. The crude product was purified by passing it through an aluminacolumn using pentane as eluent. The infrared spectrum of the purifiedmaterial was in agreement with the structure of the desired product.

EXAMPLE X Preparation of Ethylene Bis(4-t-butylazo-4-phenoxypentylcarbonate) ##EQU12##

To a solution of 4.8 grams (.0145 moles) of 4-t-butylazo-4-phenoxypentylchloroformate in 25 ml. of pentane in a 100 ml. round bottom flask wasadded a solution of 0.45 grams (.0072 moles) of ethylene glycol and 1.2grams (.0145 moles) of pyridine in 10 mls. of methylene chloride overone-half hour at 25°C. the reaction was stirred an additional one-halfhour and then 10 ml. of cold water added. The organic layer wasseparated, washed with 5% HCl, water, saturated NaHCO₃ solution, driedover anhydrous Na₂ SO₄, filtered and the solvent evaporated to leave 4.0grams (87% yield) of a light yellow liquid. The crude product waspurified by passing it through an alumina column using pentane aseluent. The infrared spectrum of the purified material was in agreementwith the structure of the desired product.

EXAMPLE XI Preparation of Ethylene Bis [4-t-butylazo-4-(octylthio)pentylcarbonate] ##EQU13##

To a solution of 7.5 grams (.02 moles) of4-t-butylazo-4-(octylthio)pentyl chloroformate in 30 ml. of pentane in a100 ml. round bottom flask was added a solution of 0.62 grams (.01moles) of ethylene glycol and 1.6 grams (.02 moles) of pyridine in 10mls. of methylene chloride over one-half hour at 25°C. The reaction wasstirred an additional one-half hour and then 10 ml. cold water added.The organic layer was separated, washed with 5% HCl, water, saturatedNaHCO₃ solution, dried over anhydrous Na₂ SO₄, filtered and the solventevaporated to leave 6.5 grams (87% yield) of a light brown liquid. Thecrude product was purified by passing it through an alumina column usingpentane as the eluent. The infrared spectrum of the purified materialwas in agreement with the structure of the desired product.

EXAMPLE XII Preparation of Ethylene Bis(4-t-butylazo-4-azidopentylcarbonate) ##EQU14##

To a solution of 4.2 grams (.015 moles) of 4-t-butylazo-4-azidopentylchloroformate in 30 ml. of pentane in a 100 ml. round bottom flask wasadded a solution of 0.475 grams (.0075 moles) of ethylene glycol land1.2 grams (.015 moles) of pyridine in 10 mls. of methylene chloride overone-half hour at 25°C. The reaction was stirred an additional one-halfhour and then 10 ml. cold water added. The organic layer was separated,washed with 5% HCl, water, saturated NaHCO₃ solution, dried overanhydrous Na₂ SO₄, filtered and the solvent evaporated to leave 3.4grams (84% yield) of a yellow liquid. The crude product containing asmall amount of unreacted chloroformate was purified by passing itthrough an alumina column using pentane as the eluent. The infraredspectrum of the purified material was in agreement with the structure ofthe desired product.

EXAMPLE XIII Preparation of 1,3-Di(t-butylazocarbonyl)benzene ##SPC20##

A. preparation of the di-t-butylhydrazide of isophthalic acid

To a solution 52.7 grams (0.6 moles) of t-butylhydrazine in 400 grams ofsaturated salt solution in a 1 liter 4-neck round bottom flask equippedwith a mechanical stirrer, thermometer, condenser, and dropping funnelwas added 50 grams (.625 moles) of 50% NaOH. The temperature wasadjusted to 10°C with an ice bath and a solution of 20.3 grams (0.1moles) of isophthaloyl chloride in 75 mls. of methylene chloride wasadded dropwise through the dropping funnel over one-half hour holdingthe temperature at 10°C ± 2°. At the end of the addition, the ice bathwas removed and the reaction was stirred an additional 21/2 hours. Awhite solid formed during the stirring period. The mixture was filteredand the filter cake was washed twice with water and twice with methylenechloride and dried overnight. The dried material weighed 23.5 grams (77%yield) and decomposed with melting at 245°C.

B. oxidation of the di-t-butylhydrazide of isophthalic acid

To a slurry of 1.5 grams (.005 moles) of the di-t-butylhydrazide ofisophthalic acid in 25 ml. of pentane was added 4.87 grams (.01 moles)of lead tetraacetate (containing 10% acetic acid) and the mixturestirred 4 hours at 35°C. At the end of the reaction period the mixturewas filtered and the pentane layer in the filtrate separated. The redpentane solution was washed with saturated NaHCO₃ solution, water, driedover anhydrous Na₂ SO₄, filtered and the pentane evaporated leaving 0.35grams (23% yield) of an orange-red liquid. The crude product waspurified by low temperature recrystallization to give an orange solidwith a melting range of 40°-45°C and gassed at 90°C. The infraredspectrum of the purified solid was in agreement with the structure ofthe desired compound.

EXAMPLE XIV Preparation of Ethylene Bis(4-t-amylazo-4-cyanovalerate)##EQU15## A. Preparation of butyl 4-t-amylazo-4-chlorovalerate

Butyl levulinate t-amylhydrazone was prepared in 90% yield by refluxingan aqueous solution of t-amylhydrazine with an equimolar amount of butyllevulinate.

To a solution of 90 grams (.316 moles) of butyl levulinatet-amylhydrazone in 150 mls. of pentane in a 500 ml. round bottom flaskwas passed 10.9 grams (.154 moles) of chlorine holding the temperatureat -20°C with a dry ice- isopropanol bath. The chlorine was added over30 minutes and then the reaction was stirred an additional 15 minutes at-20°C and filtered. The filtrate was dried and the pentane evaporatedleaving 46.6 grams of crude butyl 4-t-amylazo-4-chlorovalerate.

B. preparation of butyl 4-t-amylazo-4-cyanovalerate

To a solution of 6.2 grams (.126 moles) of sodium cyanide in 100 mls. of75% aqueous methanol in a 300 ml. flask was added 36.6 grams (.125moles) of butyl 4-t-amylazo-4-chlorovalerate dropwise over 50 minutesholding the temperature at 10°C ± 2° with a cold water bath. After theaddition was complete, the cold water bath was removed and the reactionstirred for one hour. The reaction mixture was diluted with 300 mls. ofwater and the product extracted with pentane. The pentane solution waswashed with saturated NaHCO₃ solution, dried over anhydrous sodiumsulfate, filtered, and the pentane evaporated to leave 29.7 grams (83%yield) of crude butyl 4-t-amylazo-4-cyanovalerate.

C. preparation of 4-t-amylazo-4-cyanovaleric acid

To a solution of 27.7 grams (.0938 moles) of butyl4-t-amylazo-4-cyanovalerate in 50 mls. of methanol in a 200 ml. flaskwas added 6.4 grams (.094 moles) of 85% KOH pellets and the solutionstirred for 2 hours at 25°C and for one-half hour at 35°C. The solutionwas then poured into 200 mls. of cold water and extracted with pentaneand the pentane extract discarded. The aqueous layer was acidified to apH of 3 with conc. HCl and then extracted with methylene chloride. Themethylene chloride layer was dried over anhydrous Na₂ SO₄, filtered andthe methylene chloride evaporated leaving 10.5 grams (50% yield) of ayellow liquid. The liquid was further purified by dissolving it in 10%NaOH and then precipitating it out with conc. HCl. This resulted in acreamy solid which was filtered off and dried to give 10.0 grams (M.P.60°-62°C) of 4-t-amylazo-4-cyanovaleric acid.

D. preparation of 4-t-amylazo-4-cyanovaleryl chloride

To a stirred slurry of 10 grams (.0443 moles) of4-t-amylazo-4-cyanovaleric acid in 50 mls. of pentane in a 100 ml. flaskwas added 9.37 grams(.045 moles) of PCl₅ over a 10 minute period. Afterthe addition was complete, the reaction was stirred at room temperaturefor another 50 minutes and poured into 100 mls. of ice water. Thepentane layer was separated, washed with 10% NaHCO₃ solution, dried overanhydrous Na₂ SO₄, filtered and the pentane evaporated to leave 9.0grams (84% yield) of 4-t-amylazo-4-cyanovaleryl chloride.

E. preparation of Ethylene Bis(4-t-amylazo-4-cyanovalerate)

To a stirred solution of 0.508 grams (.0082 moles) of ethylene glycoland 2 mls. of pyridine in 25 ml. pentane was added 4.0 grams (.0164moles) of 4-t-amylazo-4-cyanovaleryl chloride dropwise holding thetemperature at 25°C ± 2° with a water bath. After the addition wascomplete, the reaction was stirred for 1 hour at 24°C, diluted with 25mls. water and the pentane layer separated. The pentane solution waswashed with water, 5% HCl, water, and saturated NaHCO₃ solution, driedover anhydrous Na₂ SO₄, filtered and the pentane evaporated to leave 3.2grams (82% yield) of a clear yellow liquid. The infrared spectrum of theproduct was in agreement with the structure of the desired product.

EXAMPLE XV Preparation of Ethylene Bis(4-t-cumylazo-4-cyanovalerate)##EQU16## A. Preparation of butyl 4-t-cumylazo-4-chlorovalerate

Butyl levulinate t-cumylhydrazone was prepared in 84% yield by refluxingan aqueous solution of t-cumylhydrazine with an equimolar amount ofbutyl levulinate.

To a solution of 64 grams (0.2 moles) of butyl levulinatet-cumylhydrazone in 150 mls. of pentane in a 500 ml. round bottom flaskwas passed 7.1 grams (0.1 moles) of chlorine holding the temperature at-20°C with a dry ice-isopropanol bath. The chlorine was added over 30minutes and then the reaction was stirred an additional 15 minutes at-20°C and filtered. The filtrate was dried over anhydrous Na₂ SO₄,filtered and the pentane evaporated, leaving 33.6 grams (94.7% yield) ofbutyl 4-t-cumylazo-4-chlorovalerate.

B. preparation of butyl 4-t-cumylazo-4-cyanovalerate

To a solution of 1.77 grams (.036 moles) of sodium cyanide in 30 mls. of75% aqueous methanol in a 100 ml. flask was added 12.25 grams (.0246moles) of butyl 4-t-cumylazo-4-chlorovalerate dropwise over 50 minutesholding the temperature at 10°C ± 2° with a cold water bath. After theaddition was complete, the cold water bath was removed and the reactionstirred for one hour. The reaction mixture was diluted with 150 mls. ofcold water and extracted with pentane. The pentane solution was washedwith saturated NaHCO₃ solution, dried over anhydrous sodium sulfate,filtered and the pentane evaporated to leave 10.7 grams (90% yield) ofcrude butyl 4-t-cumylazo-4-cyanovalerate.

C. preparation of 4-t-cumylazo-4-cyanovaleric acid

To a solution of 10.7 grams (.031 moles) of butyl4-t-cumylazo-4-cyanovalerate in 30 mls. of methanol in a 100 ml. flaskwas added 2.8 grams (.035 moles) of 50% NaOH and the solution stirredfor 31/2 hours at room temperature. The solution was then poured into150 mls. of water and extracted with methylene chloride to remove thebutyl alcohol and any unreacted ester. The aqueous layer was acidifiedto pH 3 with conc. HCl and the acid extracted with methylene chloride.The methylene chloride solution was dried over anhydrous Na₂ SO₄,filtered and the methylene chloride evaporated to leave 8.4 grams (94%yield) of 4-t-cumylazo-4-cyanovaleric acid.

D. preparation of 4-t-cumylazo-4-cyanovaleryl chloride

To a stirred slurry of 8.4 grams (.029 moles) of4-t-cumylazo-4-cyanovaleric acid in 25 mls. of pentane in a 50 ml. flaskwas added 6.25 grams (.030 moles) of PCl₅ over a 5 minute period. Afterthe addition was complete, the reaction was stirred at room temperaturefor 1 hour and poured into 100 mls. of ice water. The pentane layer wasseparated, washed, with 10% NaHCO₃ solution, dried over anhydrous Na₂SO₄, filtered and the pentane evaporated to leave 5.7 grams (64% yield)of 4-t-cumylazo-4-cyanovaleryl chloride.

E. preparation of Ethylene Bis(4-t-cumylazo-4-cyanovalerate)

To a stirred solution of 0.22 grams (.004 moles) of ethylene glycol and1 ml. of pyridine in 10 mls. of methylene chloride was added 2.2 grams(.0072 moles) of 4-t-cumylazo-4-cyanovaleryl chloride dropwise holdingthe temperature at 25°C ± 2°C. After the addition was complete, thereaction was stirred for 1 hour at room temperature, diluted with 25mls. of water and the methylene chloride layer separated. The methylenechloride solution was washed with water, 5% HCl, water and saturatedNaHCO₃ solution, dried over anhydrous Na₂ SO₄, filtered and themethylene chloride evaporated to leave 1.6 grams (74% yield) of a clearyellow liquid. The infrared spectrum of the product was in agreementwith the structure of the desired product.

EXAMPLE XVI Preparation of 2,2-Bis[4-(1-(t-butylazo)cyclohexoxy)phenyl]propane ##SPC21##

To a solution of 2.28 g. (.01 moles) of 4,4-isopropylidenediphenol in 25mls. of dimethylformamide in a 100 ml. beaker was added 1.6 grams (.02moles) of 50% NaOH and the mixture stirred 30 minutes at roomtemperature. To this solution was added 4.1 grams (.021 moles) of1-t-butylazo-1-chlorocyclohexane (prepared from cyclohexanonet-butylhydrazone and chlorine) dropwise at room temperature. After theaddition was complete, the reaction was stirred 80 minutes at roomtemperature, poured into 150 ml. of water and extracted with pentane.The pentene solution was washed with water, dried over anhydrous Na₂SO₄, stirred over alumina, filtered and the pentane evaporated to leave1.8 grams (32% yield) of a straw colored solid whose melting point was66°-68°C.

The infrared spectrum of the crude product was in agreement with thestructure of the desired compound.

EXAMPLE XVII Preparation of Bis(1-t-butylazo-1,3-dimethylbutyl)ether##EQU17##

To a slurry of 1.19 grams (.0283 moles) of sodium hydride in 50 ml. ofdioxane in a 100 ml. reaction flask equipped with a magnetic stirrer,thermometer, addition funnel, and gas bubbler was added 5.25 grams(.0283 moles) of 2-t-butylazo-2-hydroxy-4-methylpentane (prepared as inWL 1352 from 2-t-butylazo-2-chloro-4-methylpentane and water) and themixture stirred for 2 hours at 25°C. At this point there was no furtherhydrogen evolution through the bubbler. To this mixture was added 5.77grams (.0283 moles) of 2-t-butylazo-2-chloro-4-methylpentane dropwiseover 15 minutes keeping the temperature at 20°C. At the end of theaddition the reaction was stirred an additional 21/2 hours at 20°C,poured into 200 ml. of ice water and extracted with pentane. The pentanesolution was washed with water, dried over anhydrous sodium sulfate,filtered, stirred over alumina for 40 minutes, filtered and the pentaneevaporated to leave 3.7 grams (34% yield) of a light yellow liquid. Theinfrared spectrum of the crude product is in agreement with thestructure of the desired product. It also shows there is some methylisobutyl ketone present.

EXAMPLE XVIII Preparation of 1,4-Bis[1-(t-butylazo)-1,3-dimethylbutoxy]butane ##EQU18##

To a slurry of 1.98 grams (.047 moles) of sodium hydride in 50 ml.dioxane in a 100 ml. reaction flask equipped with a magnetic stirrer,thermometer, addition funnel, and gas bubbler, was added 2.11 grams(.0235 moles) of 1,4-butanediol. The reaction was followed by hydrogenevolution and it required over 8 hours to complete so the reaction wasstirred overnight. The next morning, 9.59 grams (.047 moles) of2-t-butylazo-2-chloro-4-methylpentane was added dropwise at roomtemperature to the stirred salt solution. After the addition wascomplete, the reaction was stirred 4 hours and then checked by gaschromatography. Gas chromatography indicated there was a small amount ofunreacted 2-t-butylazo-2-chloro-4-methylpentane left so the reaction wasallowed to stir overnight. The next day, the reaction mixture was pouredinto 200 mls. of cold water and extracted with pentane. The pentanesolution was washed with H₂ O, dried over anhydrous sodium sulfate,filtered and the pentane evaporated to leave 9.3 grams (93% yield) of astraw yellow liquid. The crude product was purified by columnchromatography over alumina, using pentane as the eluent. The infraredspectrum of the purified material was in agreement with the structure ofthe desired product.

EXAMPLE XIX Preparation of Di(1-t-butylazo-1,3-dimethylbutyl) Succinate##EQU19##

To a slurry of 5.97 grams (.0221 moles) of sodium succinate in 75 mls.of dimethylformamide in a 200 beaker, warmed to 35°C in a water bath,was added 9.0 grams (.0442 moles) of2-t-butylazo-2-chloro-4-methylpentane dropwise. After the addition wascomplete, the reaction was stirred for 3 hours at room temperature,poured into 200 ml. of cold water and extracted with pentane. Thepentane solution was washed with water, dried over anhydrous Na₂ SO₄,filtered, stirred over alumina, filtered and the pentane evaporated toleave 6.0 grams (60% yield) of a light yellow liquid. The crude productwas purified by column chromatography using pentane as eluent. Theinfrared spectrum of the purified product was in agreement with thestructure of the desired product.

EXAMPLE XX Preparation of Bis(1-t-butylazo-1,3-dimethylbutyl)Sulfide##EQU20##

To a solution of 2.14 grams (.0271 moles) of sodium sulfide in 50 mls.of 75% aqueous methanol in a 200 ml. beaker, cooled to 15°C in a waterbath, was added 11.05 grams (.0543 moles) of2-t-butylazo-2-chloro-4-methylpentane dropwise over a 15 minute period.After the addition was complete the reaction was stirred for 90 minutesat 15°C, poured into 200 mls. of water and extracted with pentane. Thepentane solution was washed with water, dried over anhydrous sodiumsulfate, filtered and the pentane evaporated to leave 7.7 grams (77%yield) of a yellow liquid. The infrared spectrum was in agreement withthe structure of the desired product. The crude product was purified bylow temperature recrystallization from pentane.

EXAMPLE XXI Preparation of N,N'-Ethylene Bis(t-butylazoformamide)##EQU21##

To a solution of 8 g. (.046 m) of isopropyl t-butylazocarboxylate in 25ml. ethanol, cooled to 5°C, was added 1.38 g. (.023 m) ofethylenediamine dropwise over 5 minutes. The temperature slowly rose to12° and then subsided. The reaction was stirred an additional one-halfhour and the ethanol stripped off. The resulting solid was slurried inwarm benzene and filtered. The filter cake weighed 1.7 g. and had amelting point of 166°-167°C. The infrared spectrum of the yellow solidwas in agreement with that of the title product.

Evaporation of the benzene from the filtrate left 2.3 g. of a yellowliquid whose infrared spectrum was in agreement with the structure ofthe mono product t-butylazo-N-(2-aminoethyl)formamide.

EXAMPLE XXII Preparation of Di(1-t-butylazo-1-cyclohexyl) Sulfide##SPC22##

A solution of 1.56 grams (0.2 moles) of sodium sulfide in 50 ml. of 75%aqueous methanol was prepared in a 200 ml. beaker and cooled to 15°C. Tothis solution was added 8.2 grams (.0404 moles) of1-t-butylazo-1-chlorocyclohexane dropwise over a 15 minute period. Afterthe addition was complete, the reaction was stirred for 45 minutes atroom temperature and poured into 100 ml. of cold water. A solid formedand was filtered off and dried. The dried material weighed 2.2 grams(30% yield). The infrared spectrum of the product was in agreement withthe structure of the desired compound.

EXAMPLE XXIII Preparation of Di(1-t-butylazo-1-methylethyl) Sulfide##EQU22##

To a solution of 2.73 grams (.035 moles) of sodium sulfide in 30 ml. ofwater in a 200 ml. beaker was added 11.55 grams (.071 moles) of2-t-butylazo-2-chloropropane dropwise with rapid stirring over 15minutes. After the addition was complete, the reaction was stirred for 1hour at room temperature, poured into 100 ml. of water and extractedwith pentane. The pentane solution was washed with 10% HCl, water, andsaturated NaHCO₃ solution, dried over anhydrous sodium sulfate, stirredover alumina, filtered and the pentane evaporated under reduced pressureto leave 3.0 grams (30% yield) of a straw yellow liquid. The infraredspectrum of the product was in agreement with that of the desiredproduct.

EXAMPLE XXIV Preparation of1,6-Di[1-(t-butylazo)-1,3-dimethylbutylthio]hexane ##EQU23##

To a solution of 2.7 grams (.0412 moles) of 85% potassium hydroxide in50 ml. of methanol in a 250 ml. beaker was added 3.1 grams (.0206 moles)of 1,6-hexanedithiol dropwise. After the addition was complete, thereaction was stirred for 30 minutes at room temperature and then cooledto 15°C. To the cooled solution was added 8.4 grams (.0412 moles) of2-t-butylazo-2-chloro-4-methylpentane dropwise over a 20 minute periodkeeping the temperature at 15°C. After the addition was complete and theexotherm subsided, the reaction was stirred for an additional 60 minutesat room temperature, poured into 150 ml. water and extracted withpentane. The pentane solution was washed with water, saturated NaHCO₃solution and water, dried over anhydrous sodium sulfate, filtered andthe pentane evaporated to leave 8.5 grams (85% yield) of a light yellowliquid. The infrared spectrum of the product was in agreement with thestructure of the desired product.

EXAMPLE XXV Preparation of 1,4-CyclohexylenedimethylBis[2-(t-butylazo)isopropyl carbonate] ##SPC23##

A. preparation of 2-t-butylazo-2-hydroxypropane

2-t-butylazo-2-hydroxypropane was prepared by reacting aqueous sodiumhydroxide and 2-t-butylazo-2-chloropropane in t-butyl alcohol. The2-t-butylazo-2-hydroxypropane was isolated by diluting the alcoholsolution with water and extracting with pentane.

B. preparation of sodium 2-t-butylazo-isopropoxide

To a slurry of 1.96 grams (.0467 moles) of 57% sodium hydride (inmineral oil) in 70 ml. of dioxane in a 250 ml. reaction flask equippedwith magnetic stirrer, thermometer, addition funnel and gas outlet, wasadded 6.75 grams (.0468 moles) of 2-t-butylazo-2-hydroxypropane dropwiseover 20 minutes holding the temperature at 10° to 15°C. After theaddition was complete, the reaction was stirred for 30 minutes at 20°C.The sodium salt slurry was then ready to be used in step D.

C. preparation of 1,4-cyclohexylenedimethyl bis chloroformate

To a cold solution (5°C) of 15.8 grams (0.2 moles) of pyridine and 39.2grams (0.4 moles) of phosgene in 250 ml. of methylene chloride in a 1liter reaction flask was added 14.62 grams (0.1 mole) of solid1,4-cyclohexanedimethanol in small portions over 35 minutes, holding thetemperature at 0°C with an ice bath. After the addition was complete thereaction was stirred for 20 minutes at 0°C. The ice bath was removed,the reaction slowly warmed to room temperature and stirred for 30minutes and the excess phosgene stripped off by a water aspirator. A 200ml. portion of ice water was added and the reaction mixture stirreduntil the pyridine hydrochloride dissolved. The methylene chloride layerwas separated, washed with water, dried over anhydrous sodium sulfate,filtered and stripped. The product weighed 25.3 grams (93.5% yield) andwas used as such in step D.

D. preparation of 1,4-cyclohexylenedimethyl bis[2-(t-butylazo)-isopropylcarbonate]

The slurry of sodium 2-t-butylazo-isopropoxide prepared in step B wascooled to 10°C and a solution of 6.32 grams (.0233 moles) of1,4-cyclohexylenedimethyl bischloroformate in 10 ml. of methylenechloride added dropwise keeping the temperature at 15°C. After theaddition was complete and the exotherm subsided, the reaction wasstirred for 60 minutes at room temperature, poured into 200 ml. of coldwater and extracted with methylene chloride. The methylene chloridesolution was washed with water, dried over anhydrous sodium sulfate,stirred over alumina, filtered and the methylene chloride evaporatedunder reduced pressure. The residue was a light yellow liquid weighing10.0 grams (100% yield) which slowly solidified. The infrared spectrumof the product was in agreement with that of the desired compound.

EXAMPLE XXVI Preparation of S,S-1,6-Hexylene Bis[2-(t-butylazo)isopropylthiocarbonate] ##EQU24## A. Preparation of 1,6-HexyleneBis(thiochloroformate)

To a cold solution (5°C) of 15.8 grams (0.2 moles) of pyridine and 39.2grams (0.4 moles) of phosgene in 250 ml. of methylene chloride in a 1liter reaction flask, was added 15.03 grams (0.1 mole) of1,6-hexanedithiol dropwise over 25 minutes holding the temperature at 0°to 5°C with an ice bath. After the addition was complete the reactionwas stirred for 15 minutes at 5°C and 30 minutes at room temperature.The excess phosgene was stripped off by a water aspirator and theresidue washed with 200 ml. of ice cold water to remove the pyridinehydrochloride. The methylene chloride layer was separated, washed againwith water, dried over anhydrous sodium sulfate, filtered and themethylene chloride evaporated under reduced pressure to leave 27.4 grams(100% yield) of a colorless liquid.

B. preparation of S,S-1,6-Hexylene Bis[2-(t-butylazo)isopropylthiocarbonate]

A slurry of sodium 2-t-butylazo-isopropoxide was prepared as in ExampleXXV from 5.3 grams (.0368 moles) of 2-t-butylazo-2-hydroxypropane and1.55 grams (.0368 moles) of sodium hydride in 50 ml. of dioxane. Theslurry was cooled to 15°C and 5.02 grams (.0184 moles) of 1,6-hexylenebis(thiochloroformate) added dropwise over a 20 minute period, holdingthe temperature at 15°C with a cold water bath. After the addition wascomplete, the reaction was stirred for 60 minutes at room temperature,poured into 150 ml. of cold water and extracted with pentane. Thepentane solution was washed with water, saturated NaHCO₃ solution andwater, dried over anhydrous sodium sulfate, stirred over alumina,filtered and the pentane evaporated to leave 4.0 grams (44.5% yield) ofa light yellow liquid. The infrared spectrum of the product was inagreement with the structure of the desired compound.

What is claimed is:
 1. The process for preparing a polymer by freeradical initiation, the improvement which comprises polymerizing atleast one monomer containing ethylenic unsaturation in the presence of abis-azo compound having the formula:

    R--N=N--R.sub.12 --N=N--R"                                 (I)

wherein R equals R' equals (R")₃ C; (r")₃ c is C₄ -C₂₀ t-alkyl,cycloalkyl, alkylcycloalkyl, arylcycloalkyl or aralkyl wherein R" is C₁-C₈ alkyl, C₇ -C₁₂ aralkyl or C₆ -C₁₄ aryl, not more than one R' beingaromatic, and two or three of said R"s can join with the tertiary carbonatom to form a cyclo-, bicyclo- or tricyclo-hydrocarbon radical of 3-12carbons; R₁₂ is ##EQU25## R₁ and R₂ are C₁ -C₈ alkyl, C₃ -C₁₂ cyclo-,bicyclo- or tricycloalkyl, C₇ -C₁₂ aralkyl, or 5-6 membered heterocyclicwherein the hetero atom is O or N, R₁ and R₂ taken together can form aC₃ -C₁₁ alkylene diradical, one or more of each of the R₁ s and R₂ s canbe substituted with lower alkoxy, hydroxy, carboxy, loweralkoxycarbonyl, lower alkylcarbonyloxy, halo, cyano, dimethylamido orlower alkylsulfonato radicals, and R₁ can also be C₆ -C₁₄ aryl; Y" is--NHNH--, --S--, --O--, --SS--, ##EQU26## or --X"R₁₃ X"--; Z is --CN,--Cl, --Br, --X"R₅, --N₃, --SCN, --NCS, --OCN, --OOR, --OOH, --OH, --R₅,--NO₂, --NO₃, --C.tbd.CR₁₀, --C(=O)NH₂, --C(=O)OR₆, --C(=NH)NH₂,--C(=NH)OR₆, --OC(=O)H, --X"C(=X")X"R₅, --X"C(=X")R₅, --OOC(=O)R₅,##EQU27## ##SPC24##or ##EQU28## R'₁₃ is a C₂ -C₂₀ symmetrical diradicalselected from alkyl, alkylaralkyl or alkylcycloalkylalkyl groupsoptionally containing two or more non-adjacent oxygen, sulfur ornitrogen atoms in the backbone structure, cycloalkyl or, when R₁ is notphenyl or substituted phenyl, from C₆ -C₁₂ hydrocarbon aromatic; R₁₃ isa symmetrical C₅ -C₁₅ alkyl-cycloalkyl, C₂ -C₁₀ alkylene, C₃ -C₁₂cycloalkylene, C₆ -C₁₂ hydrocarbon aryl or C₈ -C₁₅ alkyl-aryl diradical;X" is oxygen or sulfur; R₅ is C₁ -C₁₀ alkyl or cycloalkyl or C₆ -C₁₂hydrocarbon aromatic; R₆ is lower alkyl; and R₁₀ is hydrogen, C₁ -C₁₀alkyl or cycloalkyl or C₆ -C₁₂ hydrocarbon aryl.
 2. The process of claim1 whereinR₁ and R₂ are C₁ -C₈ alkyl, C₃ -C₁₂ cyclo-, bicyclo- ortricycloalkyl, or C₇ -C₁₂ aralkyl, R₁ and R₂ taken together can form aC₃ -C₁₁ alkylene diradical, one or more of each of the R₁ s and R₂ s canbe substituted with lower alkoxy, hydroxy, carboxy, loweralkoxycarbonyl, lower alkylcarbonyloxy, halo, cyano, dimethylamido orlower alkylsulfonato radicals, and R₁ can also be C₆ -C₁₄ aryl; and Z is--CH, --Cl, --Br, --X"R₅, --N₃, --SCN, --NCS, --OCN, --OOR, --OOH, --OH,--R₅, --NO₂, --NO₃, --C.tbd.CR₁₀, --C(=O)NH₂, --C(=O)OR₆, --C(=NH)NH₂,--C(=NH)OR₆, --OC(=O)H, --X"C(=X")X"R₅, --X"C(=X")R₅, --OOC(=O)R₅,or##EQU29##
 3. The process of claim 2 wherein said monomer is styrene. 4.A process for preparing block copolymers by sequential free radicalinitiation which comprises:A. preparing an azo-containing polymer bypolymerizing at least one monomer containing ethylenic unsaturation inthe presence of a bis-azo compound (I) as defined in claim 1 for a timesufficient to partially decompose said bis azo compound; and B.copolymerizing said azo-containing polymer with at least one other vinylmonomer for a time sufficient to complete the decomposition of theundecomposed azo portion of said azo-containing polymer.
 5. The processof claim 4 whereinR₁ and R₂ are C₁ -C₈ alkyl, C₃ -C₁₂ cyclo-, bicyclo-or tricycloalkyl, or C₇ -C₁₂ aralkyl, R₁ and R₂ taken together can forma C₃ -C₁₁ alkylene diradical, one or more of each of the R₁ s and R₂ scan be substituted with lower alkoxy, hydroxy, carboxy, loweralkoxycarbonyl, lower alkylcarbonyloxy, halo, cyano, dimethylamido orlower alkylsulfonato radicals, and R₁ can also be C₆ -C₁₄ aryl; and Z is--CN, --Cl, --Br, --X"R₅, --N₃, --SCN, --NCS, --OCN, --OOR, --OOH, --OH,--R₅, --NO₂, --NO₃, --C.tbd.CR₁₀, --C(=O)NH₂, --C(=O)OR₆, --C(=NH)NH₂,--C(=NH)OR₆, --OC(=O)H, --X"C(=X")X"R₅, --X"C(=X")R₅, --OOC(=O)R₅,or##EQU30##
 6. The process of claim 5 wherein the monomer of step A isstyrene.
 7. The process of claim 6 wherein the vinyl monomer of step Bis methyl methacrylate.
 8. The process of claim 7 wherein theazo-containing polystyrene is prepared by heating at about 70°C. andwherein the polystyrene-poly(methylmethacrylate) copolymer is preparedby heating at about 90°C.
 9. The process of claim 8 wherein the bis-azocompound is 1,2-ethylene bis(4-t-butylazo-4-cyanovalerate).
 10. Theprocess of claim 8 wherein the bis-azo compound is 1,4-butylenebis(4-t-butylazo-4-cyanovalerate).
 11. The process of claim 8 whereinthe bis-azo compound is di(4-t-butylazo-4-cyanopentyl)sebacate.